When looking for shorts it's often just a visual thing. Like seeing a wire nut that burnt off and the wire is touching the metal frame of the appliance causing a short.

Other times I find them just by using some common sense and experience. Say for example if you have a heating element on a dryer that is shorted to the case. I would know where to look by the way the dryer was acting. In this case I could use my multimeter to check for continuity between the dryer element spades and the case to see if it was shorted.

As AJ says a lot of it is down to experience of different appliances. For example with a washing machine blowing a breaker, if it does it straight away when plugged in then you'd go to the mains filter first & disconnect that. Then it's a quick job of testing with a Multimeter or Megger to find if it's shorted or not, if not then you move to the next item in the line & do the same thing. If it's dropping the breaker further into the programme then work out what should be coming in then, i.e Inlet valve, Pump, Heater etc & disconnect / test that part. Just a process of elimination.

If a dryer, and it blows the breaker right when you plug it in, it's the heating element shorted. If anything else, you have to determinewhat the item was switching into when it blew. If a refrigerator and you turn the defrost timer to defrost and it blows the breaker, the short is in the defrost circuit. If a washer or fridg. would be helpful to put it on a extension cord with breaker. Sometimes you can find a short with an ohmmeter. Most of the time though, the short only happens when you put 115 volts to the item, 9 volt ohmmeter will not indicatea short in that case.